For many years, meat has been sold as sausages or loaves wherein meat product is stuffed into a casing. The casings were originally the intestine of the animal. In more recent years, synthetic casings have been offered in the market.
In the context of this specification, the term, meat product, is understood to mean a wide assortment of meat preparations, including ground beef, dismembered poultry, etc. These various assortments would obviously present a wide consistency due to variation in content of fat, moisture, size of meat fiber, size of meat chunks, etc.
The quality of the meat product is determined not only by the meat but by the quality and homogeneity of the loaf. Homogeneity is determined by the stuffing process, i.e., how well the meat product is mixed and how effectively air is removed from the meat product which otherwise collects to form voids. In former times, stuffing was performed manually so that inhomogeneity, compared to present standards, was very poor.
As the demand for the number and quality of meat product loaves increased, machines have been developed to stuff the meat product. The first machines, illustrated in FIG. 1, included an air-actuated ram to stuff meat product drawn down from a conical hopper and out through a "horn". The casing is placed over the horn to receive the meat product that is passed through the horn. The upper large rim of the conical hopper is typically twelve feet above the floor so that one of the inconveniences of using this machine is having to lift the meat product up to this height in order to fill the hopper.
As shown in FIG. 2, in the next generation of machines the piston was replaced by a vane pump or small screw, and a vacuum was added adjacent to the horn so that the casing was partially evacuated and the meat product was thereby drawn into the casing.
As shown in FIG. 3, in order to facilitate loading the meat product by not having to lift the meat product up to the rim, machines were developed with an evacuated upper chamber into which meat product was drawn by vacuum. The chamber contained a large screw which directed the meat product toward the chamber exit so that the meat product was stuffed through the horn into the casing using a combination screw and vacuum. Although the vacuum in the chamber helps to homogenize the meat product by withdrawing entrapped air, the use of a large screw (auger) to force the meat product into the exit port compacts the meat product and thereby obstructs the desired homogenizing of the meat product. These machines have the additional problem that fat tends to collect on the blade leading to inhomogeneity of the meat product. The construction of these machines takes frequent cleaning of the screw (necessitated by the collection of fat thereon) which is very time-consuming and inconvenient.
None of the machines discussed in the foregoing paragraphs addresses the problem of preparing meat product and stuffing the meat product into a casing where the meat product has been homogenized to an optimum consistency regardless of the initial condition of the meat product with respect to content of moisture, fat, fiber length, air pockets or gross inhomogeneity.